The present invention relates generally to technology for detecting an analyte. In various embodiments, the invention relates to devices for measuring pH.
pH, or potential of hydrogen, is a measure of the acidity or alkalinity of a solution. The pH of a solution is determined by the concentration, or more rigorously speaking the activity of hydrogen ions (H+), also referred to as protons, within the solution. As the concentration of protons increases, the solution becomes more acidic. Conversely, the solution becomes more basic as the concentration of protons within the solution decreases. The concentration of protons within a solution has traditionally been measured with a glass electrode probe connected to an electronic meter that displays the pH reading.
A traditional pH probe or glass electrode is a type of ion-selective electrode made of a fragile, doped glass membrane that is sensitive to protons. This pH-responsive glass membrane is the primary sensing element in this type of probe. Protons within the sample solution bind to the outside of the glass membrane thereby causing a change in potential on the interior surface of the membrane. This change in potential is measured against the constant potential of a reference electrode such as the silver/silver chloride reference electrode. The difference in potential is then correlated to a pH value by plotting the difference on a calibration curve. The calibration curve is created through a tedious, multistep process whereby the user plots changes in potential for various known buffer standards. Most traditional pH sensors are based on variations of this principle.
The accuracy and reliability of traditional pH glass electrodes are unstable and therefore require careful, regular calibration and care involving tedious, time-consuming processes requiring multiple reagents and a well trained technician. The special properties and construction of the glass electrodes further require that the glass membrane be kept wet at all times. Thus, routine care of the glass probe requires regular performance of cumbersome and costly storage, rinsing, cleaning and calibration protocols by a well trained technician to ensure proper maintenance and working condition of the probe.
In addition to tedious maintenance, traditional glass electrodes are fragile thereby limiting field applicability of the glass electrode. In particular, the fragile nature of the glass electrode is unsuitable for use in food and beverage applications, as well as use in unattended, harsh or hazardous environments. Accordingly, there is a need in the art for a pH probe that addresses and overcomes the limitations of the traditional pH glass electrode. Such a pH probe device is disclosed herein.